Incoloy 800HT Blind Flanges — UNS N08811 Top Creep-Grade Blind Manufacturer
Tesco Steel & Engineering forges Incoloy 800HT blind flanges — ASTM B564, UNS N08811, EN 1.4959 — to ASME B16.5 Class 150–2500 from ½″ to 24″ NB and to ASME B16.47 up to 60″. The trio's top grade differs by a sum: aluminium plus titanium controlled to 0.85–1.20%, so the precipitation that resists creep arrives on schedule in service — buying the best stress-rupture life in the 800 family while the cold-tensile sheet stays identical to 800H's (a purchasing trap worth knowing: two certificates with the same strength table are not the same grade). Carbon floored at 0.06–0.10% — the notch that lets HT heats dual-certify as H — grain mandated coarse and measured. The alloy licensors write by name for the hottest reformer-outlet pigtails, manifolds and headers toward 900°C. Below the creep line: straight 800. Oxidation past the family: Inconel 601. Facings: BLRF, BLFF or BLRTJ. Every lot with EN 10204 3.1/3.2 MTC — carbon, Al+Ti sum and grain size measured. ISO 9001:2015, made in Mumbai, India — exported to 50+ countries.
Incoloy 800HT · ASTM B564 · UNS N08811EN 1.4959 · X8NiCrAlTi32-21Al+Ti Sum 0.85–1.20% — The SignatureBest Rupture Life of the 800 TrioReformer Outlets Toward 900°CGrain ASTM ≤5 — Measured & CertifiedASME B16.5 ½″–24″ · Class 150–2500EN 10204 3.1 / 3.2 · ISO 9001:2015
Incoloy 800HT Blind Flanges — Specifications at a Glance
What is an Incoloy 800HT Blind Flange?
The top creep grade — defined by a sum. A solid forged disc of iron-nickel-chromium alloy (ASTM B564 / UNS N08811 / EN 1.4959) with no bore — the family base with carbon floored at 0.06–0.10%, grain mandated coarse (ASTM ≤5), and the signature: Al+Ti summed to 0.85–1.20%, guaranteeing the in-service precipitation that buys the best stress-rupture life of the trio. Cold mechanicals identical to 800H's (450/170 MPa) — the difference lives at 850°C, not on the tensile sheet. The grade licensors name for the hottest reformer-outlet components. Dimensions per ASME B16.5 / B16.47 in RF, FF and RTJ facings; EN 10204 3.1 with all three defining values measured.
Also searched as: Alloy 800HT blind flange, N08811 blind, 1.4959 blind flange, X8NiCrAlTi32-21 blind, SB564 800HT blind, reformer pigtail blind flange — all refer to the product on this page. See also the siblings Incoloy 800 / 800H blind flanges, the wet-corrosion cousin 825, the next rung Inconel 601, and the facing pages BLRF / BLFF / BLRTJ.
One Controlled Sum, the Family's Best Curves
The Elements That Harden In Service
Aluminium and titanium form fine gamma-prime-type precipitates at operating temperature — the superalloy trick, dosed lightly. 800HT is the only member of the trio that guarantees enough of them: individually 0.15–0.60% each, but summed to a mandatory 0.85–1.20%.
Why the Sum, Not the Windows
800 and 800H allow the same individual windows without policing the total — a lean heat can pass both and still precipitate weakly. The controlled sum closes that gap, and appears on our certificates as a measured value.
The 0.06 Notch
HT's carbon floor sits one notch above H's — entirely inside the H window. Every conforming HT heat automatically satisfies H: the foundation of dual-certified 800H/800HT stock, one MTC carrying both numbers plus the values that earn them.
The hottest outlets, toward 900°C — licensor-named duty
The purchasing trap: all three creep-side certificates can show the same cold strength table — 800H and 800HT are identical there by specification. The grade lives in the chemistry lines: compare the carbon floor and the Al+Ti sum, not the tensile numbers — and when the datasheet says N08811, an N08810 certificate is not a substitute.
Incoloy 800HT Chemical Composition (UNS N08811)
Element
Ni
Cr
Fe
C
Al
Ti
Al+Ti
Mn
Si
S
Weight %
30.0–35.0
19.0–23.0
≥39.5
0.06–0.10
0.15–0.60
0.15–0.60
0.85–1.20
≤1.5
≤1.0
≤0.015
Three certificate lines define this grade against its siblings: the carbon floor, the Al+Ti sum and — not in this table — the grain number (ASTM ≤5), measured metallographically and reported like an element. The family's iron floor (≥39.5%) carries over; our MTCs carry all three defining values, and PMI reads the Ni-Cr-Fe signature on every piece.
Mechanical Properties — Identical Sheet, Different Metal
Property
ASTM B564 N08811 Requirement (Solution Annealed)
Tensile Strength
≥ 450 MPa (65 ksi) — identical to 800H by specification
Yield Strength (0.2%)
≥ 170 MPa (25 ksi)
Elongation
≥ 30%
Grain Size
ASTM 5 or coarser — mandatory, measured, on the MTC
Condition
Solution annealed (deliberately hot cycle) — stated on certificate
The Real Specification
Stress-rupture life at 800–900°C — the best in the family, quantified in the licensors' design curves; the tensile table is not what this grade is bought for
High-pressure hydrogen & syngas practice — ring softer than groove
Incoloy 800HT Blind Flange Specifications
Incoloy 800HT / UNS N08811 Blind Flanges are available in the following specifications:
Material Grade
Incoloy 800HT — ASTM B564 / ASME SB564 (UNS N08811); dual-certified 800H/800HT on request; EN 1.4959 designation where required
Heat Treatment
Solution annealed, coarse grain — grain size (ASTM ≤5) measured and reported on every lot
Size
1/2"NB to 24"NB per ASME B16.5; 26"–60" per ASME B16.47; EN 1092-1 to order
Class
150#, 300#, 400#, 600#, 900#, 1500#, 2500# — rated on the grade's own nickel-alloy B16.5 lines
Facings
Raised Face (BLRF), Flat Face (BLFF), Ring Type Joint (BLRTJ) with groove per B16.20
Service Span
The hottest code-creep duty, ~600–900°C — reformer outlets, pigtails, headers; sulphur-bearing hot gas excluded; rapid-cycling duty deserves a design review
Surface Finish
Pickled or natural machined — no paint; segregated alloy handling throughout
Modifications
NPT-tapped centre (thermocouple / test / vent), lifting provisions — machined & certified at the works
Testing
Tension & chemistry per heat — carbon floor, Al+Ti sum and iron floor verified; grain size measured; PMI routine
Certification
EN 10204 3.1 (standard) / 3.2 witnessed — all three defining values on every MTC
Why Incoloy 800HT Blind Flanges Are Specified
The Licensor Named It
Reformer-outlet stress-rupture curves were generated on material with the guaranteed sum and coarse grain — so the datasheet says N08811, and the certificate must answer line for line.
The Hottest Stations
Pigtails, outlet manifolds and headers at 850–900°C, campaigns measured in years — where 800H's margins thin and HT's curves keep working.
Same Rupture Clock, Closure Included
A blind on an outlet header lives at the same temperature for the same decade as the manifold — a lesser-grade closure becomes the joint's shortest-lived member and sets the turnaround date.
One Family, One Works
800 below the line, 800H for the general creep range, 800HT at the summit, dual-certified where useful — quoted together, certificate by certificate.
Know the Map
General creep range at friendlier cost: 800H. Below ~600°C: straight 800. Oxidation & cycling beyond: 601. Wet & sour: 825. Facings: BLRF / BLFF / BLRTJ.
Specification Notes — Getting 800HT Right
Three details buyers miss.Read the chemistry, not the strength table: 800H and 800HT certify to identical cold minimums — the grade lives in the carbon floor and the Al+Ti sum, and an N08810 certificate is not a substitute where the datasheet says N08811. All three defining values belong on the MTC: measured carbon, measured Al+Ti sum, measured grain size — ours carry all three on every lot. Don't buy the summit below the treeline: for the general 600–850°C creep range, 800H serves identically at friendlier cost, and below ~600°C straight 800 is the better tool — we quote the rung the duty actually needs.
How Our Incoloy 800HT Blind Flanges Are Manufactured
1
Forging — cut billet of the spectro-verified N08811 heat — carbon floor, Al+Ti sum and the 39.5% iron floor confirmed — is hot-forged into the solid disc blank with full heat traceability and segregated alloy handling.
2
Solution annealing — the deliberately hot cycle that coarsens the grain to ASTM 5 or beyond; furnace charts retained against the heat number.
3
Grain-size verification — measured metallographically and reported on the certificate, beside the measured Al+Ti sum — the values the licensors' curves assume.
4
Machining & facing — faces, OD and drilling to ASME B16.5 / B16.47; RF serrations, flat face or RTJ groove gauged per B16.20; NPT taps machined where ordered.
5
Testing & finishing — tension test and chemistry against the heat; PMI on every piece; pickled and marked with standard, grade, size, class and heat number.
6
Certification & packing — EN 10204 3.1 MTC (3.2 witnessed on request) with measured carbon, Al+Ti sum and grain size; faces protected, palletised or crated sea-worthy — no carbon-steel contact in transit.
Where Incoloy 800HT Blind Flanges Are Used
The hottest stations of the code-creep world: reformer outlet pigtails, manifolds and headers in ammonia, methanol and hydrogen plants; the highest-temperature process heaters; ethylene and cracking hardware; elevated-temperature code-case circuits. Production below:
8″ Class 300 Blind Flange — Machined at Our WorksForged Blind Flanges — Ready for DispatchIncoloy 800HT Flanges — Same Grade, Protected Stock
Incoloy 800HT Blind Flange Dimensions
Blind dimensions are class-governed — identical across material grades. Full charts:
How to Specify & Order an Incoloy 800HT Blind Flange
Five elements — the three defining certificate values are the 800HT-specific ones:
1
Size & standard — e.g. 6″ NB ASME B16.5, or the B16.47 series for 26″ and above.
2
Pressure class & facing — Class 150–2500; RF, FF or RTJ (with ring number) to match the mating flange.
3
Grade — ASTM B564 UNS N08811 (Incoloy 800HT), or dual-certified 800H/800HT where one stock must serve both; EN 1.4959 designation where required.
4
Service & certification — state design temperature and atmosphere; NPT tap size if a thermocouple or test blind; PMI or 3.2 witnessing as specified; EN 10204 3.1 with measured carbon, Al+Ti sum and grain size — our standard.
An Incoloy 800HT blind flange is a solid forged disc of the top creep grade in the 800 family — the iron-nickel-chromium base with carbon floored at 0.06-0.10%, a mandatory coarse grain, and the signature control: aluminium plus titanium summed to 0.85-1.20% — certified to ASTM B564 as UNS N08811, EN 1.4959. It closes the hottest reformer-outlet systems — pigtails, manifolds and headers running toward 900°C — where licensor specifications write the grade by name for its stress-rupture life. Dimensions follow ASME B16.5 from ½ inch to 24 inch and ASME B16.47 beyond, in raised face, flat face and ring joint facings.
What is the Al+Ti sum, and why is it the grade's signature?
It is a controlled dose of the elements that harden the metal in service. Aluminium and titanium form fine gamma-prime-type precipitates at operating temperature — the same particles that strengthen the superalloys — and 800HT is the only member of the trio that guarantees enough of them: individually 0.15-0.60% each, but summed to a mandatory 0.85-1.20%. Straight 800 and 800H allow the same individual windows without policing the total, so a lean heat can pass both and still precipitate weakly. The controlled sum is what buys the best stress-rupture numbers in the family — and it appears on our certificates as a measured value.
800HT and 800H show identical strength tables — what is the actual difference?
The purchasing trap worth naming. Both grades certify to the same cold minimums — 450/170 MPa, 30% elongation — so two MTCs can look interchangeable while describing different metals. The difference lives where the tensile table cannot show it: in stress-rupture life at 800-900°C, where 800HT's guaranteed Al+Ti precipitation outlasts 800H's by a margin the licensors' design curves quantify. The rule for buyers: compare the chemistry lines (the Al+Ti sum and the 0.06 carbon floor), not the strength lines — and when a specification says N08811, an N08810 certificate is not a substitute, however identical its mechanicals look.
Why is 800HT's carbon floored at 0.06 rather than 0.05?
One notch of deliberate overlap engineering. The 0.06-0.10% window sits entirely inside 800H's 0.05-0.10%, which means every conforming 800HT heat automatically satisfies the H grade's carbon requirement — the foundation of the dual-certification practice mills use: melt to the HT windows (carbon 0.06-0.10, Al+Ti 0.85-1.20, coarse grain) and the heat certifies as both N08811 and N08810 on one MTC. One inventory serves both specifications, and we supply exactly such dual-certified forgings on request, with the measured values that earn both numbers reported.
What is the chemical composition of Incoloy 800HT (UNS N08811)?
Nickel 30.0-35.0%, chromium 19.0-23.0%, iron 39.5% minimum — the family's iron floor — carbon 0.06-0.10%, aluminium 0.15-0.60%, titanium 0.15-0.60%, with the aluminium-plus-titanium sum controlled to 0.85-1.20%, manganese ≤1.5%, silicon ≤1.0%, sulphur ≤0.015%. Alongside the chemistry sits the equal requirement of grain size: ASTM 5 or coarser, measured and reported. Three certificate lines define this grade against its siblings — the carbon floor, the Al+Ti sum and the grain number — and our MTCs carry all three.
What are the mechanical properties of Incoloy 800HT blind flanges?
Per ASTM B564 in the solution-annealed condition: tensile strength 450 MPa (65 ksi) minimum, yield strength 170 MPa (25 ksi) minimum, elongation 30% minimum — identical to 800H, and deliberately below straight 800's 520/205, because the coarse grain that serves creep softens the cold sheet. The grade's real property is the one the licensors design on: stress-rupture life at 800-900°C, the best in the family courtesy of the guaranteed Al+Ti precipitation. As with 800H, the room-temperature table is not what anyone buys this grade for.
What temperature range does an Incoloy 800HT blind flange cover?
The hottest end of the family's territory: code-creep duty from roughly 600°C to 900°C, with oxidation resistance toward 980°C and the carburizing-atmosphere tolerance of the whole 800 clan. Its designed home is the top of that band — the reformer-outlet components at 850-900°C where 800H's margins thin and HT's rupture curves keep working. Below 600°C it serves no better than its cheaper siblings; beyond its window, the handoffs are Inconel 601 for oxidation and cycling, and the specialised superalloys where creep demands outrun the family altogether.
Why do reformer licensors write N08811 into their specifications by name?
Because the outlet components are designed on rupture curves, and the curves belong to specific certified chemistry. Pigtails, outlet manifolds and headers run at the family's hottest sustained temperatures for campaigns measured in years; the licensors' stress-rupture data — the basis of every wall-thickness calculation — was generated on material with the guaranteed Al+Ti sum and coarse grain, so the specification names the UNS number that guarantees them. A closure on that manifold inherits the naming: the licensor datasheet says N08811, and the certificate must answer it line for line.
Why does the grain size matter as much as the chemistry?
Because creep flows along grain boundaries, and the specification closes that path. At 850°C the metal deforms largely by boundary sliding and diffusion: the more boundary area, the faster the flow. The mandatory coarse grain — ASTM 5 or coarser, from a deliberately hot solution anneal — shrinks the network, and together with the precipitation chemistry it forms the rupture life the grade is bought for. That is why the grain number is measured metallographically and reported on the MTC like an element: a fine-grained heat with perfect chemistry is still not 800HT.
What service conditions does Incoloy 800HT dislike?
The family list, sharpened at the hot end. Sulphur-bearing gases attack it — fuel analysis on the enquiry, as for every nickel-bearing grade. Wet chloride chemistry belongs to Incoloy 825: no molybdenum here. The coarse grain trades away some fatigue and thermal-shock tolerance, so rapid-cycling duty deserves a design review rather than reflex specification. And below the creep line the premium buys nothing — straight 800's finer grain is the better tool there, and we will say so on the quotation rather than sell the top grade where the base grade serves.
A blind flange on a pigtail manifold — why must it be 800HT?
Because the closure lives on the same rupture clock as the manifold. A blind on an outlet header sees the same 870°C, the same hydrogen-rich gas and the same decade-long campaign as the pressure parts around it — and a closure certified to a lesser grade becomes the joint's shortest-lived member, with its distortion or leak path setting the turnaround date. The standing system logic applies with the temperature turned up: one line-class material, one set of allowables, one certificate trail from manifold to closure — and at these temperatures, the audit checks the Al+Ti sum and grain size on every one.
What facings are Incoloy 800HT blind flanges made with?
All three: raised face (BLRF) — the default — flat face (BLFF) for mating flat-faced and lined equipment, and ring type joint (BLRTJ) for the high-pressure hydrogen and syngas practice of its plants, the ring chosen softer than the groove. Each facing has its own page on this site. At 800HT's working temperatures, joint design is creep design: gasket systems have their own ceilings and bolt-load relaxation over year-long campaigns deserves the same hours-at-temperature thinking as the flange. NPT-tapped thermocouple and test blinds are machined and certified at the works.
Where are Incoloy 800HT blind flanges used?
The hottest stations of the code-creep world: steam-reformer outlet pigtails, manifolds and headers in ammonia, methanol and hydrogen plants; the highest-temperature process heaters and their manifolding; ethylene and cracking hardware at the top of the family's range; and elevated-temperature code-case circuits in HTGR and concentrated-solar service. 800HT blinds close those systems as isolations, spare-nozzle blanks and tapped test points — certified to the carbon floor, the Al+Ti sum and the grain size the licensor's curves assume.
Which standards cover Incoloy 800HT blind flanges?
The material standard is ASTM B564 (UNS N08811) with ASME SB564 as the boiler-code twin — the nickel-alloy forging standard — alongside B408 for rod and B409 for plate in the same family, and EN 1.4959 / X8NiCrAlTi32-21 as the European designation; the siblings certify as N08800 (alloy 800) and N08810 (800H), with 800H/800HT dual certification common practice. Dimensions follow ASME B16.5 for ½"-24" and ASME B16.47 for 26"-60". A complete specification reads: 'Blind Flange, RF, 6", ASME B16.5 Class 300, ASTM B564 UNS N08811 (Incoloy 800HT)' — and our EN 10204 certificates state it exactly that way, measured carbon, Al+Ti sum and grain size included.
Who manufactures Incoloy 800HT blind flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, forging Incoloy 800HT / ASTM B564 / UNS N08811 / EN 1.4959 blind flanges — with alloy 800, 800H and dual-certified 800H/800HT material alongside — from ½" to 24" NB per ASME B16.5 in Classes 150-2500 and to 60" per ASME B16.47, solution annealed with grain size verified (ASTM 5 or coarser), the carbon floor and Al+Ti sum measured on every heat, pickled, PMI-verified on every piece, certified to EN 10204 3.1/3.2 on every lot, in raised face, flat face and ring joint facings — alongside the full Incoloy, Inconel and nickel-alloy blind range. Exported to more than 50 countries.
